There are known in the art navigation devices and navigation systems for searching for a route from a desired departure point to a departure point using map data and road data to provide guidance to a user. Such navigation devices and navigation systems that have been implemented include navigation devices mounted in an automobile and used for providing route guidance to the driver, and communication-type navigation systems that send a route searching request to a route searching server using a cellular telephone as a navigation terminal and receive the result to received route guidance.
In particular, a communication-type navigation system is a system in which a cellular telephone or another mobile terminal is used as a navigation terminal, and which is also used as a navigation system for a pedestrian. The navigation system for a pedestrian preferably has a route guidance function that includes transportation systems, and there are also navigation systems that keep transportation system lines and operating time data in a route searching server, and in addition to searching and providing guidance for a walking route, have a function for providing route guidance (candidate train for boarding) from a desired departure station to a desired destination station in addition to searching and providing guidance for a walking route. There are also transportation guidance systems for receiving delivery of and displaying transportation lines, time tables, boardable trains, and other information from an information delivery server that does not include route searching for a walking route.
A common navigation device, route-searching device using in a communication-type navigation system, and route-searching means are disclosed in, e.g., Patent Reference 1 (Japanese Laid-open Patent Application No. 2001-165681). This navigation system is configured so as to send departure point and destination point information from a portable navigation terminal to an information delivery server, and to search for and provide guidance for a route that matches the search conditions from road network and transportation network data in the information delivery server. Examples of the search conditions that may be used as one of the search conditions include movement means from the departure point to the destination point, e.g., walking, automobile, and railroad in combination with walking.
The information delivery server is provided with link cost information (distance and required time) of all links as a database in which the connecting points and curve points of the roads (routes) of the map data are nodes and routes that connect the nodes are links. The information delivery server is capable of referring to the database, sequentially searching for a link that reaches from the departure point node to the destination point node, and providing guidance about the shortest route to the portable navigation terminal by following the nodes and links that minimize the link cost information to obtain a guidance route. A technique referred to as the label determination method or the Dijkstra method is used as the route searching technique. A route-searching method that uses the Dijkstra method is disclosed in Patent Reference 1.
An invention related to a route-searching system is disclosed in Patent Reference 2 (Japanese Laid-open Patent Application No. 2000-258184) in which the rectilinear distance from the departure point and the destination point to the station of the transportation system to be used and the rectilinear distance from the destination point to the station of the transportation system to be used are calculated using the latitude and longitude information, the average cost is calculated using the rectilinear distance as a variable, and all of the stations of the transportation systems included in the range of costs specified in the average cost are obtained to determine a walking route.
Route-searching systems for searching routes using transportation systems are provided with an operation timetable database in which operation timetable data of transportation systems have been organized into a database on the basis of departure time, departure point, destination point, arrival time, and other route searching conditions designated by the user; and are provided with data in which the transportation network has been organized into a database on the basis of the above. The route-searching systems are configured to reference these databases, connect a departure point and a destination point while including transit changes (transfers), sequentially follow usable transportation means (individual trains and shuttle buses) as a route, and present one or a plurality of candidates for route guidance (departure station, destination station, course, train, and other transportation means) that matches the route searching conditions. Route searching conditions that can be designated commonly further include required time, number of transit changes, fares, and other conditions.
Guidance systems have also been proposed for carrying out retrieval and guidance related to transportation systems in which a cellular telephone or another terminal connects to an information delivery server that provides guidance related to line information and time table information of transportation systems; specifies a desired departure station, departure time, destination station, or the like; receives delivery of information about boardable lines, trains, trams, and other transportation means; and displays the information on the terminal device. Generally, when such use is carried out using a terminal device, a configuration used in which the URL (uniform resource locator), domain name, or the like for specifying the location of information desired for download is inputted in the terminal device, an information delivery server (information site) specified by the address is accessed, and the desired information is downloaded.
Route search data in a navigation system or the like that performs a route search or provides route guidance that makes use of a transportation system has stations on a transportation line as nodes and station-to-station intervals as bidirectional links in the same manner as road network data in a navigation system for a vehicle or a navigation system for a pedestrian, and the nodes and links are organized as network data. Additionally, the operating times and required time of each link are added as link cost data for each transportation means operated on a transportation line. There are also systems that furthermore add fare data and provide guidance together with the fare for the guidance route that has been searched.
The earth is divided into time zone regions as reference times based on Greenwich Mean Time (GMT), and time table data of transportation systems are created using the local time (time that includes time difference from GMT) in accordance with the time zone of each region. A common route-searching system assumes that route searches are essentially carried out in a single time zone, the case in which the departure point and destination point belong to different time zones not being taken into account.
In other words, in the case that the time zones of the departure point and the destination point are different, a problem is presented in that the destination point arrival time is not displayed in the time referenced by the time zone to which the destination point belongs in the case that the departure point time has been set and a search carried out using the common route-searching system described above; and conversely, the departure time is not displayed in the time referenced by the time zone to which the departure point belongs in the case that the destination point arrival time has been set and a search has been carried out.
In regard to movement means such as a train in which the departure point and destination point are established, a route search is carried out using different reference time data, i.e., time data in which the time zone to which the departure point belongs is used as a reference, and time data in which the time zone to which the destination point belongs is used as a reference. Therefore, a problem is presented in the process of searching for a route in that the route search must be carried out while determining the time zone of each node (a point on the route) and converting the time between different time zones in the case that the route spans different time zones; and the route search cannot be easily carried out.
An example of a route-searching system in which consideration is given to differences in time zones is disclosed in Patent Reference 3 (Japanese Laid-open Patent Application No. 2005-121425) as an invention of an onboard navigation device. Even if a road exists on a guidance route that involves travel time restrictions and the road belongs to a time zone different from the departure point, the onboard navigation device disclosed in Patent Reference 3 is capable of converting the restricted time using the time difference to carry out a route search.
In other words, the onboard navigation device has a storage device for storing link data that includes the time restriction information of the links constituting a road on a map, and map data that includes time zone information for determining the time zone to which the links belong. The departure point and destination point are set and a recommended route is searched from the departure point to the destination point using the map data. The route search is configured to exclude links having time restrictions in terms of the estimated time of arrival at the link on the basis of the time restriction information and the time zone information. A link that spans different time zones is handled as a plurality of links divided along a time zone boundary so that the links do not span different time zones.
[Patent Reference 1]    Japanese Laid-open Patent Application No. 2001-165681 (FIGS. 1 and 2)    Japanese Laid-Open Patent Application No. 2000-258184 (FIGS. 4 and 6)    Japanese Laid-Open Patent Application No. 2005-121425 (FIGS. 10 and 11)